Enable by default threaded compositing on windows and FCM on mac

chrome/browser/chrome_gpu_util.cc

Index: chrome/browser/chrome_gpu_util.cc
diff --git a/chrome/browser/chrome_gpu_util.cc b/chrome/browser/chrome_gpu_util.cc
index 90efc1246768600b631690ea153dc4a5f08a06d2..d5b37fb96270e98b96dff3132ab52669c4b4ebd6 100644
--- a/chrome/browser/chrome_gpu_util.cc
+++ b/chrome/browser/chrome_gpu_util.cc
@@ -74,7 +74,7 @@ void InitializeCompositingFieldTrial() {
   scoped_refptr<base::FieldTrial> trial(
     base::FieldTrialList::FactoryGetFieldTrial(
         content::kGpuCompositingFieldTrialName, kDivisor,
-        "disable", 2012, 12, 31, NULL));
+        "disable", 2017, 12, 31, NULL));

[Alexei Svitkine (slow), 2012/09/13 13:37:45]

The goal of the expiry date is to set an expectation of when you're likely to
have gotten all you needed out of the field trial and are no longer interested
in it. That way, the system can automatically disable it at that point and also
gives a hint that the code can be deleted.

I doubt you expect to still be using this trial in 2016, so please set this to
something more reasonable.

 
   // Produce the same result on every run of this client.
   trial->UseOneTimeRandomization();
@@ -82,31 +82,27 @@ void InitializeCompositingFieldTrial() {
   base::FieldTrial::Probability force_compositing_mode_probability = 0;
   base::FieldTrial::Probability threaded_compositing_probability = 0;
 
+  // Threaded compositing mode isn't feature complete on mac or linux yet:
+  // http://crbug.com/133602 for mac
+  // http://crbug.com/140866 for linux
+
+#if defined(OS_WIN)
+  // threaded-compositing turned on by default on Windows.
+  // (Windows XP is excluded explicitly in ShouldRunCompositingFieldTrial)
+  threaded_compositing_probability = 3;

[Nico, 2012/09/13 01:49:37]

nit: Set this to kDivisor instead

+#elif defined(OS_MACOSX)
+  // force-compositing-mode turned on by default on mac.
+  force_compositing_mode_probability = 3;

[Nico, 2012/09/13 01:49:37]

same

+#elif defined(OS_LINUX)
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
-  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
-      channel == chrome::VersionInfo::CHANNEL_BETA) {
-    // Stable and Beta channels: Non-threaded force-compositing-mode on by
-    // default (mac and windows only).
-#if defined(OS_WIN) || defined(OS_MACOSX)
-    force_compositing_mode_probability = 3;
-#endif
-  } else if (channel == chrome::VersionInfo::CHANNEL_DEV ||
-             channel == chrome::VersionInfo::CHANNEL_CANARY) {
-    // Dev and Canary channels: force-compositing-mode and
+  if (channel != chrome::VersionInfo::CHANNEL_STABLE &&
+      channel != chrome::VersionInfo::CHANNEL_BETA) {
+    // On channels < beta, force-compositing-mode and
     // threaded-compositing on with 1/3 probability each.
     force_compositing_mode_probability = 1;
-
-#if defined(OS_MACOSX) || defined(OS_LINUX)
-    // Threaded compositing mode isn't feature complete on mac or linux yet:
-    // http://crbug.com/133602 for mac
-    // http://crbug.com/140866 for linux
-    threaded_compositing_probability = 0;
-#else
-    if (!CommandLine::ForCurrentProcess()->HasSwitch(
-            switches::kDisableThreadedCompositing))
-        threaded_compositing_probability = 1;
-#endif
+    threaded_compositing_mode_probability = 1;

[Alexei Svitkine (slow), 2012/09/13 13:37:45]

The variable name you use elsewhere is |threaded_compositing_probability|
(without the "mode"), so this won't compile.

   }
+#endif
 
   int force_compositing_group = trial->AppendGroup(
       content::kGpuCompositingFieldTrialForceCompositingEnabledName,